Severe valvular heart disease (VHD) affects 1 out of 40 adults in the United States, and is responsible for approximately 28,000 deaths per year. Aortic valves consist of 3 film-like cusps with an average thickness of 300-700 μm. The main composition of the valvular extracellular material (ECM) is type I collagen and elastin in a 4:1 dry weight ratio which orchestrate the passive opening and closing of the aortic leaflets to direct blood flow. Dysfunctional heart valves are life-threatening as the diseased valvular tissues are unable to perform the normal physiological requirements. Among all VHD, aortic valve disease has a mortality rate of about 65%. The treatment usually necessitates surgical replacement by mechanical or tissue bioprosthetic valves. Commonly used mechanical heart valves have adequate durability but are often thrombogenic and require life-long anti-coagulant therapy. Bioprosthetic collagen-based tissue valves from porcine valves or bovine pericardium mimic the anatomy of native valves, however, early valve degeneration, and 50% postoperative failure occur within 12-15 years. Therefore, a nonthrombogenic and durable alternative is desperately needed in the field.
Successful heart valve grafts should be both durable and functional. Basic anatomical and physiological requirements need to be considered to fabricate structurally similar and mechanically robust synthetic heart valve grafts. Approaches to overcome the pathological failure modes should be taken into consideration in order to select graft composites that are biocompatible, slowly degradable and durable, capable of promoting adequate cell growth and tissue remodelling, while being non-thrombogenic.